Such a capped electric lamp is known from U.S. Pat. No. 4,542,316.
In the known lamp, the seal of the lamp vessel has a saw cut between the current conductors in order to give each current conductor its own glass envelope which is connected to the seal and which is separated from the other one by a slit. The object of this is to increase the electric creepage path between exposed portions of the current conductors. This enhances the possibility of the lamp being ignited at a comparatively high voltage of, for example, several kV. A further increase in the creepage path is achieved in that a partition wall in the lamp cap divides the lamp cap into compartments and enters the slit.
The known lamp cap is of the G38 type, a type having comparatively heavy metal pins whose centrelines are 38 mm removed from one another. Lamp caps of this or a similar type can be used in standardized lampholders. As a result, the known lamp can be used as a replacement for traditional halogen lamps, which do not require a high ignition voltage, in an environment comprising a standardized lampholder.
The known lamp cap is built up from two identical ceramic parts which are joined together when the lamp vessel is provided, together with contacts, metal pins, and mica plates which are to form the partition wall, and are fastened to one another with cement. For several applications, moreover, the electric element must be given a defined position relative to the lamp cap. This renders the assembly of the known electric lamp complicated.
European Patent Application EP 0 455 295 A1 discloses a high-pressure discharge lamp in which two saw cuts are made in the seal of the lamp vessel at a distance from one another and in which the glass between these saw cuts is broken away so as to make a slit. A fold is present in the base portion of the ceramic lamp cap of the lamp, extending to inside the slit.
A similar lamp is known from British Patent GB 2 100 404 B. Here a glass tube surrounding each of the current conductors is connected to the seal so as to form a slit between said current conductors. An incision is present running from the base portion of the ceramic lamp cap of the lamp which partly coincides with the slit. This lamp and the lamp of the cited EP 0 455 295 A1 have contact pins which are comparatively close together. They are designed for use in a lampholder which has a partition wall which enters the incision or the fold, respectively. Lampholders for lamp caps of the G38 type do not have such a partition wall.